Assessment of health risk and identification of pollution sources of heavy metals in water in Chongqing’s wastewater treatment plants based on ICP-MS

Abstract

Chongqing is located upstream of the Yangtze River and within the Three Gorges Reservoir Area. Boasting a dense hydrological network comprising interconnected rivers, tributaries, and reservoirs, the condition of the natural environment in Chongqing is intrinsically linked to drinking water safety. To evaluate the regional distribution, pollution levels, health risks, and sources of 12 heavy metals, a total of 90 water samples (30 influent sewage, 30 effluent sewage, and 30 tap water samples) were systematically collected from 30 wastewater treatment plants (WWTPs) across Chongqing. Heavy metal pollution index (HPI), heavy metal evaluation index (HEI), degree of contamination (CD), and health risk assessment were utilized in this study to present the findings of a thorough assessment of heavy metal contamination in the region. Meanwhile positive matrices factorization (PMF) was applied to ascertain sources of heavy metals in influent sewage. The results showed that sewage treatment diminished pollutant concentrations. After treatment, Zn, Hg, Pb, and Cr were the primary contaminants in the effluent sewage, significantly surpassing the Class I standard limit for surface water in China. The primary sources of sewage contamination were anthropogenic activities, including agriculture, industry, and transportation. The cumulative health risk from carcinogenic heavy metals surpassed the permissible danger threshold. Cr was responsible for majority of health hazards. These findings indicate the priority control requirements for various heavy metals and establish a scientific foundation for the hierarchical management strategy of heavy metals, optimization of wastewater treatment processes, and the assurance system for drinking water safety.